As is well-known, the atmosphere can be very smoky in workshops in which welding is performed. Apart from the smells, eye-irritant, and general unpleasantness, the smoke and fumes carry traces of carcinogens and other hazards to a welding operator's health.
Two approaches to the problem have been addressed: (a) by allowing fumes from all the torches to enter the shop atmosphere and then installing an air cleaning system for the whole workshop, or (b) by adding a hood to the torch itself, at source, near the arc, to draw in the fumes before they can escape into the workshop.
The latter approach is theoretically the more attractive, since it is generally more economical to remove contaminants where they are concentrated rather than after they have been allowed to dissipate. However, hitherto, the problem of extracting the fumes actually at source, i.e. with a hood that fits on the torch, has not been fully solved.
Those prior torches which have had good fume extraction have had hoods which interfered with the welder's ability to see the weld and its surroundings. But if the hood was positioned so that visibility was not impaired, the fume extraction performance of the hood was very poor.
One of the difficulties also is that if the hood is located too close to the arc, and/or if the fume extraction is too strong, not only the fumes but the carbon dioxide or other gas supplied to the arc may be drawn away, thus permitting oxidation to take place, and making the weld porous.